This invention relates to a motor drive apparatus, e.g., the drive apparatus of a motor for opening and closing the power window of a vehicle.
A mechanism (power window) for opening and closing a window by the driving force of a motor is employed in many vehicles. Though one such mechanism which controls the forward and reverse rotation of the motor (the opening and closing of the window) directly by an operating switch is available, a variety of electronically controlled power window systems have recently come into widespread use. For example, one mechanism is such that if a foreign object of some kind becomes caught between the window frame and the window glass when the window is being closed, this is sensed and control is carried out to reverse the rotation of the motor and open the window. Another such mechanism remotely controls the opening and closing of the window by wireless communication.
In any case, many systems use relays to drive the window opening and closing motor in the forward and reverse directions and to halt the rotation thereof. Consequently, if an accident occurs in which the vehicle falls into the sea or into a river and sinks, the motor may be actuated, owing to malfunction of the relays, regardless of the fact that neither operation of the switch nor electronic control is carried out. For example, if the motor rotates in the reverse direction and the window closes, the driver and any passengers will become trapped inside the vehicle.
A motor drive apparatus using relays for the power window of a vehicle according to the prior art will be described with reference to FIG. 6a. 
The window of a vehicle is opened and closed by the rotation of a motor 1. There are provided a relay 2 for rotating the motor 1 in the forward direction (to open, i.e., lower, the window), and a relay 3 for rotating the motor 1 in the reverse direction (to close, i.e., raise, the window).
The relay 2 includes a relay coil 2a and relay contacts 2b. The relay contacts 2b include a normally open contact (make contact or a contact) NO and a normally closed contact (break contact or b contact) NC. The relay 3 includes a relay coil 3a and relay contacts 3b. The relay contacts 3b includes a normally open contact NO and a normally closed contact NC.
The contacts (or terminals) NO of these relay contacts 2b, 3b are connected to the line of a power supply E1, and the contacts (or terminals) NC of these relay contacts are connected to ground. Common terminals C of these relay contacts 2b, 3b are connected to positive and negative terminals ma, mb, respectively, of the motor 1. The motor rotates forward when a positive voltage is applied to the terminal ma and in reverse when a positive voltage is applied to the terminal mb.
The relay coil 2a of relay 2 is connected between the line of a power supply E2 and ground and in series with a window-opening operating switch 4. Similarly, the relay coil 3a of relay 3 is connected between the line of the power supply E2 and ground and in series with a window-closing operating switch 5.
The two operating switches 4, 5 are illustrated as being separately provided as operating switches. In actuality, however, the switches 4 and 5 usually are equipped with a common operating knob capable of being rocked back and forth. The structure used is such that the switch 4 is turned on when the knob is swung in one direction and the switch 5 is turned on when the knob is swung in the other direction.
Single-pole, double-throw contacts (transfer contacts or break-make contacts) are illustrated as the relay contacts 2b, 3b. It goes without saying, however, that the apparatus may have parallel-connected normally open contacts NO and normally closed contacts NC, as shown in FIG. 6b. 
If the operating switch 4 is turned on, the relay coil 2a is energized to actuate the relay contacts 2b. The common terminal C in the relay contacts 2b is connected to the normally open contact NO and separates from the normally closed contact NC. Accordingly, current flows from the line of power supply E1 to the positive terminal ma of motor 1 through the normally open contact NO and common terminal C of the relay contacts 2b, and current that flows out of the negative terminal mb of motor 1 flows to ground through the common terminal C and normally closed contact NC of relay contacts 3b. As a result, the motor 1 rotates in the forward direction and the window is opened. When the operating switch 5 is turned on, current from the power supply E1 flows to ground through the contacts 3b, motor 1 and contacts 2b, so that the motor 1 rotates in the reverse direction and the window is closed.
The above-described motor drive apparatus is such that energization of the relay coils 2a, 3a is controlled directly by turning the operating switches 4, 5 on and off. There is also an apparatus of the type in which the states of operating switches are judged by a single-chip microcomputer or the like and the energization of the relay coils is controlled based upon the judgment made.
FIG. 7 illustrates an example of a conventional motor drive circuit that relies upon such control by microcomputer. A controller (circuit) 13 typified by a microcomputer is provided in the diagram of FIG. 7. An operating switch 14 has a common terminal C and two normally open contacts NO1, NO2. Under ordinary conditions, the common terminal C is not connected to either the contact NO1 or the contact NO2. The common terminal C is connected to ground. A power-supply voltage E3 is applied on the contacts NO1, NO2 via pull-up resistors 15, 16, respectively. Under ordinary conditions, these voltages are applied to corresponding input ports of controller 13.
In comparison with the circuits of FIGS. 6a and 6b, the circuit of FIG. 7 has relay control transistors 11, 12 instead of the operating switches 4, 5 connected in series with the relay coils 2a, 3a, respectively. The control terminals 11, 12 are on/off controlled by the controller 13. Under ordinary conditions, these transistors 11, 12 are held in the off state.
If an operating knob is moved or swung in one direction so that the contact NO1 of operating switch 14 is connected to the common terminal C, the contact NO1 is brought to ground level. The ground-level voltage is sensed by the controller 13. The controller 13 outputs a control signal (H level) that turns on the transistor 11, and the relay coil 2a is energized to rotate the motor 1 in the forward direction. If the operating knob is swung in the other direction, the contact NO2 of operating switch 14 is connected to the common terminal C. The controller 13 senses the ground level at the contact NO2 and outputs a control signal that turns on the transistor 12, as a result of which the relay coil 3a is energized to rotate the motor 1 in the reverse direction.
The above-described motor drive apparatuses are such that if the vehicle falls into the sea, a lake or a river and the apparatus becomes submersed, there is a possibility that a phenomenon (so-called leakage) will occur in which, depending upon the quality of the water, a current flows into either contact of the operating switches (switches 4, 5 or switch 14) despite the fact that the operating knob has not been operated. As a consequence, there is the possibility that problems will arise, such as the motor 1 being rotated in the forward or reverse direction, the reversely rotating motor being stopped or control over the motor being lost, regardless of the fact that the operating knob has not been operated.
In general, a relay has a hysteresis characteristic, in which the voltage for actuating the relay (the voltage, which shall be referred to as the xe2x80x9cactuating voltagexe2x80x9d, applied to a relay coil in order to turn on a normally open contact or turn off a normally closed contact) is higher than the voltage (which shall be referred to as the xe2x80x9crestoration voltagexe2x80x9d) for returning the relay to the ordinary state. That is, if a voltage that exceeds the actuating voltage is applied to the relay coil, the relay is actuated; when the applied voltage falls below the restoration voltage, the relay returns to the original state. Further, there is a variation in the actuating voltage or restoration voltage from one relay to another. In other words, even if relays of the same type are used, the actuating voltage and restoration voltage thereof differ slightly depending upon the individual relay.
Undesirable phenomena that can occur if a vehicle (strictly speaking, the portion of the motor drive apparatus in which the relays or switches, etc., are placed) is submersed will be described keeping the above-mentioned facts in mind.
If leakage develops across the ends of operating switch 4 or 5 in FIG. 6a, this is equivalent to a resistor (referred to as a xe2x80x9cleakage resistorxe2x80x9d) being connected in parallel with the operating switch. Such a situation is illustrated in FIG. 8. Here an operating switch SW is the operating switch 4 or 5, and a relay coil CL is the relay coil 2a or 3a. The power-supply voltage is represented by the character E, and a leakage resistor is represented by the characters RL. Since leakage current flows through the resistor RL, a coil voltage VCL is produced across the relay coil CL. The coil voltage VCL changes in dependence upon the state of submersion (impurities contained in the water) and becomes extremely unstable.
If the coil voltage VCL resulting from leakage is higher than the actuating voltage of the relay, a phenomenon occurs in which the relay is actuated to rotate the motor despite the fact that the operating switch has not been operated. For example, if the actuating voltage of the relay 2 for opening the window is higher than the actuating voltage of the relay 3 for closing the window and the coil voltage VCL due to leakage is between the actuating voltages of the two relays 2, 3, then only relay 3 will be actuated and the window will close. If the window closes, this will impede the escape of passengers from the submersed vehicle.
In a case where the coil voltage VCL due to leakage is higher than the actuating voltages of both the relays 2 and 3, both of the relays 2 and 3 are actuated. Since the normally open contacts NO in the relay contacts 2b, 3b of the relays 2, 3 are both turned on, the power-supply voltage E1 is impressed across the motor 1 and the motor 1 does not rotate. Even if the operating switch 4 or 5 is turned on under these conditions, the motor 1 will not rotate. Thus the operating switches have absolutely no effect.
If the coil voltage VCL due leakage declines and falls below the restoration voltage of either of the relays 2, 3 under these conditions, this relay is restored. Since the other relay is not restored and remains actuated, the motor 1 rotates in the forward or reverse direction. For example, if the restoration voltage of relay 2 is higher than the restoration voltage of relay 3, only relay 2 is restored and the motor 1 rotates in the reverse direction, as a result of which the window is closed.
Further, if a submersion accident occurs and the coil voltage VCL due to leakage surpasses the restoration voltage of the relay 3 when one of the operating switches, e.g., the operating switch 5, has been turned on by the driver or by a passenger to close the window, the relay 3 continues to operate so as to close the window even if the operating switch 5 is turned off.
These undesirably phenomena can occur in the circuit of FIG. 7 as well. The operating switch 14 develops leakage owing to submersion, a current flows to ground through the resistor 15 and contact NO1, and a current flows to ground through the resistor 16 and contact NO2. The voltages that appear at the contacts NO1 and NO2 are sensed by the controller 13. If the controller 13 recognizes that the voltage at contact NO1 or NO2 or the voltages at both of these contacts is/are less than a threshold voltage level, the controller outputs a control signal that turns on the transistor 11 or 12 or both of these transistors. As a result, the motor 1 rotates in the forward direction or reverse direction or a state is attained in which the motor cannot be controlled by the operating switch 14.
Though it is considered that the foregoing problems will be solved by adopting a waterproof structure for the operating switches, this is not easy to accomplish in actual practice. The reason is that it is difficult technically to adopt a waterproof structure solely for the switch contacts while maintaining the operating knob of the operating switches in a rockable state and exposing a portion of the knob. Even if achieving this is feasible, an increase in cost results.
An object of the present invention is to prevent the occurrence of a situation in which the motor operates against the will of the operator owing to relay malfunction caused by submersion in water.
Another object of the present invention is to so arrange it that a motor is made to operate in accordance with the will of the operator even if a submersion accident occurs.
A motor drive apparatus according to the present invention has a relay mainly for operating to rotate a motor in a forward direction, and a relay mainly for operating to rotate a motor in a reverse direction. A motor forward-rotation command or reverse-rotation command is applied by an operator through an operating portion (operating knob, operating switch, etc.). The forward-rotation relay or reverse-rotation relay is actuated in response to the forward-rotation command or reverse-rotation command (e.g., directly in response to the operating switch being turned on or off, or through a microprocessor or other control circuit), thereby causing the motor to rotate in the forward or reverse direction.
In accordance with the present invention, the motor drive apparatus has submersion sensing means for sensing that at least an operating portion of the motor drive apparatus has become submersed; first malfunction sensing means for sensing that one relay of the above-mentioned relays, which is for rotating the motor in a predetermined one direction, has been actuated; and first forcible control means for actuating the other relay in response to submersion being sensed by the submersion sensing means and actuation of the one relay being sensed by the first malfunction sensing means.
If submersion is sensed and actuation of the one relay is sensed, then the other relay also is actuated by the first forcible control means. Since the relay for forward rotation of the motor and the relay for reverse rotation of the motor are both actuated, the motor ultimately assumes a state in which in will not rotate in either the forward or reverse direction (e.g., a state in which the same potentials appear at both ends of the motor). This makes it possible to prevent the occurrence of a situation in which the motor rotates in one direction against the will of the operator owing to malfunction of one relay caused by submersion.
A pair of the malfunction sensing means and a pair of the forcible control means may be provided. Specifically, the motor drive apparatus according to the present invention further includes second malfunction sensing means for sensing that the other relay has been actuated, and second forcible control means for actuating the one relay in response to submersion being sensed by the submersion sensing means and actuation of the other relay being sensed by the second malfunction sensing means.
This makes it possible to prevent the occurrence of a situation in which the motor rotates in the other direction owing to malfunction of the other relay caused by submersion.
The submersion sensing means and malfunction sensing means can also be implemented by a single means, as will be described later.
In a preferred embodiment of the present invention, there is provided a shorting circuit for establishing a short circuit across a relay coil of the relay that rotates the motor in the one direction, in operative association with manipulation of the operating portion so as to generate a command that rotates the motor in the other direction.
By virtue of the shorting circuit, the ends of one malfunctioning relay are shorted, as a result of which this relay is restored to the ordinary state. Accordingly, when the operator applies a command that actuates the other relay, only this other relay is actuated (or has already been actuated by the forcible control means) and the motor runs in accordance with the will of operator.
The present invention can also be expressed in the followed manner: Specifically, the present invention provides a motor drive apparatus having two relays for rotating a motor in a forward or reverse direction by supplying power to the motor, wherein the relays are actuated to rotate the motor in the forward or reverse direction in accordance with the operating state of an operating portion that is for commanding forward or reverse rotation of the motor, characterized by having submersion malfunction sensing means for outputting a submersion malfunction detection signal upon sensing that the motor drive apparatus has become submersed and that one relay of the above-mentioned relays, which is for rotating the motor in one direction, has been actuated; and forcible control means for energizing a relay coil that is for actuating the other of the above-mentioned relays, irrespective of the operating state of the operating portion, in response to output of the submersion malfunction detection signal.
The submersion malfunction sensing means outputs the submersion malfunction detection signal upon sensing that the motor drive apparatus has become submersed and that one relay, which is for rotating the motor in one direction, has been actuated. If the submersion malfunction detection signal is output, the forcible control means energizes a relay coil in order to actuate the other relay regardless of the operating state of the operating portion.
If a relay malfunctions owing to leakage brought about by submersion, the submersion malfunction detection signal is output and the other relay also is actuated by being energized by the forcible control means. Both relays ultimately are actuated, therefore, to establish a state in which the motor cannot rotate in either direction. Accordingly, it is possible to prevent, with a high degree of reliability, the occurrence of a situation in which the motor rotates in either direction against the will of the operator owing to malfunction of only one of the relays caused by leakage resulting from submersion.
The present invention can be expressed all-inclusively as follows: Specifically, the present invention provides a motor drive apparatus having two relays for rotating a motor in a forward or reverse direction by supplying power to the motor, wherein the relays are actuated to rotate the motor in the forward or reverse direction in accordance with the operating state of an operating portion that is for commanding forward or reverse rotation of the motor, characterized by having submersion sensing means for outputting a submersion detection signal upon sensing that the motor drive apparatus has become submersed; and forcible control means for actuating both of the relays, irrespective of the operating state of the operating portion, in response to output of the submersion detection signal.
The submersion sensing means outputs the submersion detection signal upon sensing that the motor drive apparatus has become submersed. If the submersion detection signal is output, the forcible control means energizes both of the relay coils regardless of the operating state of the operating portion. If a submersion accident occurs, therefore, the submersion detection signal is output, both relays are actuated by forcible control exercises by the forcible control means and the end result is that a state in which the motor cannot rotate in either direction is established. Accordingly, it is possible to prevent, with a high degree of reliability, the occurrence of a situation in which the motor rotates in either direction owing to actuation of only one of the relays caused by leakage resulting from submersion.
In an embodiment, the motor is a motor for driving an opening and closing body of a vehicle. By applying the motor drive apparatus of the present invention to a motor that drives an opening and closing body (a power window or sunroof, etc.) of a vehicle, a malfunction in which the opening and closing body is actuated against the will of a passenger is prevented even in the event of an accident in which the vehicle becomes submersed.
According to another embodiment, rotation of the motor in one direction is rotation in a direction that closes the opening and closing body, and rotation of the motor in the other direction is rotation in a direction that opens the opening and closing body.
In the case of the direction in which a relay coil forcibly actuated by the forcible control means opens the opening and closing body of the vehicle, a malfunction especially in a direction in which the opening and closing body of the vehicle is closed is prevented. This makes it possible to maintain the opening and closing body in the open state reliably even in a case where a vehicle submersion accident has occurred. This enables the passengers to escape from the passenger compartment easily, thereby enhancing the safety of the vehicle.